Anisotropic Segre [(11)(1,1)] dark energy following a particular equation of state

TL;DR

This paper explores the use of an anisotropic equation of state for dark energy within Bianchi and FLRW cosmological models, revealing scenarios of vacuum energy evolution, big bounce behavior, and transitions between vacuum states.

Contribution

It introduces a novel anisotropic equation of state for dark energy and analyzes its implications in both anisotropic and isotropic cosmological models.

Findings

Spacetimes evolve towards vacuum energy or de Sitter configurations.

Anisotropic models exhibit big bounce-like behavior.

Isotropic models show transitions between vacuum states and radiation-like regimes.

Abstract

A generally anisotropic equation of state originally derived in the context of Newman-Janis rotating systems allows for vacuum energy at a specific density. In this paper we examine the possibility of using that equation of state for cosmological dark energy. We treat the case of large scale ordering of the directions of the energy-momentum tensor eigenvectors with a Bianchi cosmological model, and treat the case where the ordering is random on small scales with an effectively isotropic FLRW system. We find particular spacetimes which evolve towards a vacuum energy/ de Sitter like configuration in either case. In the anisotropic Bianchi case, the system can have behavior reminiscent of big bounce cosmologies, in which the matter content approaches vacuum energy at large scale factor and can behave in a variety of ways at small scale factor. For particular conditions in the effectively isotropic case, we can evolve between true and false vacuum configurations, or between radiation like and vacuum energy configurations. We also show how some simpler equations of state behave under the same assumptions to elucidate the methods for analysis.